Known in the art are devices for loading and unloading containers at plants for treating substances, such as plants for drying products, called freeze-dryers.
Freeze-dryers are used for drying products, typically pharmaceutical or food products. Pharmaceutical products are placed in the freeze-dryer in glass containers, on flat shelves situated one above another to form the equivalent of shelving. Most freeze-dryers have means for moving said flat shelves vertically, so that they can either be stacked or placed one by one at a particular loading height.
The freeze-drying process, particularly for pharmaceutical products, requires maximum sterility of the product and its container but also of its manipulating elements, such as loading and unloading systems and treatment installations. For this reason, the parts of such installations that are in contact with the product and its container are normally placed in clean rooms, whose space is usually very small for reasons mainly associated with the high maintenance cost of such rooms. Before loading the freeze-dryer it is also normal to have all the manipulating elements undergo a cleaning and sterilisation process.
The design of loading and unloading devices for treatment plants such as freeze-dryers must take into account the space restriction of clean rooms and the need to have simple equipment that can be disassembled easily to clean and sterilise its parts. Moreover, again due to the need to ensure product hygiene, it should be taken into account that such devices must avoid to the utmost extent loading and unloading parts that remain inside the freeze-dryer during the treatment, as access into the freeze-dryer is difficult and means that such parts cannot be cleaned adequately.
U.S. Pat. No. 5,129,162 discloses a method and apparatus for loading and unloading freeze-drying apparatus including at least one placement surface adapted to receive containers. The containers are placed on a table top of a transfer table, and the transfer table is brought into proximity with the placement surface in a chamber of a freeze-drying apparatus. A retractable frame assembly, movably secured to the transfer table, is used to transfer the containers from the transfer table top to the placement surfaces.
The device of the cited US patent has the disadvantage that it occupies a large space in clean rooms since it comprises a formatting table and a transfer table that has to be brought into proximity with the freeze-drying apparatus once loaded with containers. Furthermore, the working speed is extremely slowly because during the loading and unloading process a large number of steps must be taken.
Patent ES 2130818 discloses a device for loading and unloading treatment equipment, such as freeze-dryers, which makes automatic loading and unloading of containers possible by means of a set of two encapsulated hydraulic cylinders, each of which has at its end a bar mounted transversally to the direction of travel of the cylinders. One of these cylinders is mounted at the rear part of the freeze-dryer and traverses the wall of the freeze-drying chamber by means of a sealed mechanical feedthrough, in such a way that the bar attached to its end moves over the freeze-dryer shelves from the rear part of the shelves. The other cylinder is mounted at the front part of the freeze-dryer, beside a conveyor belt which feeds the containers. The rear and front cylinder bars form an enclosure into which the rows of containers from the conveying device are loaded one by one, during the loading process, or from the freeze-dryer shelf during the unloading process.
In the loading process, for each row of containers loaded the two cylinders and bars move over the loading zone by a distance equivalent to the diameter of a container, and next, only the cylinder and front bar move back to the departure position to permit the entry of a new row of containers. This operation is repeated as many times as there are rows of containers that fit on a shelf of the freeze-dryer, until the loading zone is full. The loaded containers are then placed in the freeze-dryer by the joint action of both cylinders and bars, which move them aligned on said loading zone until they are situated on the shelf of the freeze-dryer.
In the unloading process, the two cylinders and bars move over the shelf of the freeze-dryer until all the containers have been placed aligned in the unloading zone, from which they are pushed by the rear cylinder and bar towards the conveyor belt which unloads them.
The device described in patent ES 2130818 has several disadvantages, as outlined below.
The sealed mechanical feedthrough for the rear cylinder which traverses the freeze-dryer chamber increases the risk of leaks in the chamber and, therefore, also increases the danger of lack of product and process sterility.
Furthermore, the presence of this part in the rear part of the freeze-drying chamber makes it impossible to mount the device on an existing freeze-dryer, since the space inside a freeze-dryer is very small and does not permit the mounting of new parts for which provision has not been made in advance. The mechanical modifications which this addition would entail for the freeze-dryer chamber would also be too costly.
The working cycle of the device of the above-mentioned patent has the disadvantage of having a time lag upon completion of loading of each shelf, as the rear cylinder and bar have to retract to their initial positions in order to allow the vertical movement of the loaded shelf and to await the positioning of a new shelf for loading containers. This time lag between the loading of shelves can be lengthy, and this has a negative effect on the efficiency of the device.
Utility model DE 20102879U1 describes a device for loading and unloading containers in treatment installations which resolves the disadvantages mentioned above.
Said device includes two moving parts to make automatic loading and unloading of containers possible. On the one hand, there is a cylinder and bar which during the loading process move the containers from the conveyor belt to a fixed platform, and on the other hand a flexible sheet which unfurls from a cylindrical drum. Both moving parts are external to the treatment installation and place themselves outside the installation during the treatment process, so they have the advantage that they do not hinder cleaning and sterilisation of the freeze-dryer.
In the loading process, for each row of containers loaded the cylinder and bar move over the fixed platform by a distance equivalent to the diameter of a container, and next, move back to the starting position in order to allow the entry of a new row of containers. The flexible sheet unfurls and advances intermittently by a distance equal to the diameter of a container each time it receives a row of containers from the fixed platform, so that when it reaches the flat shelf of the treatment installation it advances over its surface. This operation is repeated as many times as there are rows of containers that fit on a flat shelf of the treatment installation, until the loading zone made up of the fixed platform and the unfurled section of flexible sheet is full of containers.
The loaded containers are subsequently placed in the enclosure of the installation by the joint action of the cylinder and bar and of the flexible sheet. Said cylinder and bar push the containers deposited on the fixed platform as far as the flexible sheet, at the same time as said sheet moves to place itself entirely on a flat shelf of the treatment installation. Next, once all the containers are on the flexible sheet and the latter is on the flat shelf, said sheet retracts, sliding under the containers, while the bar and the cylinder keep the containers fixed and aligned on the flat shelf.
The unloading process is carried out by the flexible sheet itself. Firstly, said sheet is placed on the flat shelf, sliding under the containers, while the cylinder and the bar remain at the front part of the flat shelf acting as a stop. Secondly, said sheet retracts, thereby pushing the containers deposited on it towards the fixed platform and the conveyor belt which unloads them.
The working cycle of the device described also has the advantage of having no times lag, as upon completion of loading of each flat shelf, and while the vertical travel of the loaded shelf is taking place, containers can be loaded onto the fixed platform of the device.
The device described in utility model DE 20102879 U1 nevertheless has several disadvantages, as outlined below.
The working speed is limited, because during the loading process both the travel of the containers on the fixed platform and the travel of the flexible sheet itself with the loaded containers is carried out without the presence of a bar to act as a stop for said containers.
Indeed, it has to be taken into account that the intermittent advance of the flexible sheet is a source of continual movements of the containers deposited thereupon, which means that the working speed has to be reduced in order to prevent such containers from spilling or falling.
The unloading process has the disadvantage of not being completely automatic, since at the end of the unloading process it requires the assistance of an operative to push the last rows of containers left on the fixed platform towards the conveyor belt.
As has been described, the unloading process is carried out by the flexible sheet itself when, as it retracts, it pushes the containers deposited on it towards the fixed platform and the conveyor belt that unloads them. When the flexible sheet is left free of containers, however, and even if it does retract, it cannot push the last rows of containers to be unloaded, since those containers are deposited only on the fixed platform. Therefore, an operative must push said last rows of containers by means of a bar or the like so that they can be unloaded by the conveyor belt.
Another disadvantage of the device described in the German Utility Model is that it is an equipment that cannot be disassembled easily in order to submit its parts to cleaning and sterilisation each time the treatment installation is loaded.
Indeed, in order to carry out cleaning and sterilisation of the flexible sheet which winds and unwinds around the cylindrical drum, said sheet has to be unfurled completely, which involves a number of disadvantages. For instance, there is the need to have space to spread out the sheet, which can be large; such space can be difficult to achieve in the light of the space-restriction that exists in clean rooms.